The invention is directed to methods for connecting a semiconductor to a substrate, or for the after-treatment of a semiconductor-to-substrate connection by pressing, and is also directed to arrangements for the implementation thereof.
Semiconductors are often connected to metal substrates to increase the mechanical stability and for better heat elimination. Bonding techniques such as gluing or soldering that are fast, inexpensive, and that can be implemented in fully automated fashion are usually employed for that purpose. The temperature resistance and the resistance to thermal shocks, however, are thereby limited, particularly given chip sizes having an edge length of several millimeters. The thermal and electrical resistance of the glue also has a disadvantageous effect when gluing semiconductors and, in particular, in power semiconductors.
A high-strength connection can be achieved with low thermal and electrical resistance by pressure sintering a silver powder layer according to EP-A-242 626, corresponding to U.S. Pat. No. b 4,810,672, issued Mar. 7, 1989, incorporated herein. A pressing power is thereby respectively applied by rigid dies on the parts to be connected. In this pressing process, the upper side of the semiconductor is entirely contacted by a pressure-transmitting, solid medium.
EP-330 896, corresponding to U.S. Pat. No. 4,903,886, issued Feb. 27, 1990, and EP-330 895, corresponding to U.S. Pat. No. 4,903,885, issued Feb. 27, 1990, both incorporated herein, further disclose that the substrate and the semiconductor be embedded in an elastic centering form of, for example, silicone rubber which transmits the pressure power of a movable die since it completely fills out the interior of a receptacle chamber in which the substrate and the semiconductor member are situated. The pressure power remains when the sintering pressure is reached. In this known pressing process, a contact between a solid medium and the upper side of the semiconductor member is needed. However, contaminations of the semiconductor surface frequently arise.